Information storage disks generally have planar surfaces with a center hole therethrough for placement on a motor driven hub. When the disk is placed on the motor driven hub, it is necessary to use an assembly that holds the disk securely thereon. If the drive containing the disk is dropped, there is a tendency for the disk to disengage from the hub which may result in damage to the disk or other parts of the disk drive.
Many arrangements have previously been devised to hold a disk onto a motor hub. One problem inherent with the use of a clamp to secure a disk in place lies in the fact that disks and clamps do not have perfectly planar engaging surfaces. Therefore, upon placement of a disk having an imperfectly planar surface between a hub flange having an imperfectly planar surface and a clamp having an imperfectly planar surface, disk distortion can occur. As the clamp presses down upon a disk planar surface, the disk is "squeezed" between the clamp and the flange. This squeezing action causes any surface irregularities to distort the planar surface of the disk at the clamping interface and this distortion extends radially outward into the read/write surface. Any distortion of the disk read/write surface may result in lost or distorted data.
A disk clamping device is disclosed in U.S. Pat. No. 4,347,599 to Vitale, issued on Aug. 31, 1982. The Vitale device provides a spindle clamp assembly for securely clamping an information disk in a precisely centered position upon a rotatable drive spindle. An expansible sleeve is provided to cooperate with a wedge collet for uniform radial expansion of the sleeve and thus centering of the disk upon a spindle. Spring loaded locking means are also provided to secure the disk between a clamping surface and a flange on the motor hub. The Vitale device precisely centers a disk yet is subject to the very problem identified above of potential distortion of the disk by the squeezing action between the clamping surface and the flange.
Another clamping device is disclosed in U.S. Pat. No. 4,539,614 to Thompson, issued on Sep. 3, 1985. The Thompson device includes a clamping lever for use with a floppy disk drive to align and clamp the disk to a drive spindle. Activation of a handle causes a rotational clamping device to move from a position spaced apart from the disk to a position on the disk for clamping of the disk between the clamping device and a hub portion. Thus, this device also "squeezes" the disk between the clamping device and the hub portion which may cause distortion of the read/write surface of the disk.
Another apparatus for centering and clamping a disk is disclosed in U.S. Pat. No. 4,502,136 to Rickert et al., issued on Feb. 26, 1985. The Rickert device uses an elevator to raise a disk into centering contact with a drive spindle. As the elevator raises the disk into centered engagement with the spindle, a magnet on a portion of the elevator engages a metallic ring on a spindle platform with the disk therebetween. The magnet and metallic ring thus clamp the disk therebetween securing the disk in position. This device, like the Vitale and the Thompson devices, can cause distortion of the read/write surface of the disk by the squeezing of the disk therebetween. Thus, it would be advantageous to provide a method and apparatus for securing a disk to a drive hub which reduces the likelihood of distortion of the disk and therefore reduces the occurrence of inaccuracies in the read/write data of the disk.